Observable changes in the electrical and optical characteristics of individual molecules adsorbed on a conductor or semi-conductor caused by electrical and/or optical excitation or de-excitation of electrons within such molecules can be used as signals to carry information, as is disclosed in the above-referenced application. Such a molecule or molecules can be observed using optical spectrophotometric methods to obtain a Raman spectrum which reveals the condition or state of energization of a molecule, including, for example, the location of one or more electrons, especially free electrons, therein, the energization level of the molecule and/or electron(s), and the nature of the incident electromagnetic beam, e.g. laser light, used directed to the molecule(s) in the Raman spectrophotometric process. The Raman spectrum so derived for a given condition/energization of the molecule(s) ordinarily will include one or more Raman lines of respective intensities the whole of which may be considered a "fingerprint" of the state of the molecule.
Such molecular devices are characterized by a high speed of response. As is disclosed in such application, switching times may be on the order of 10.sup.-13 second and even to 10.sup.-15 if the molecule exhibits tunnelling.
Dyes have been used in the past to obtain information about the state of nerves. In such case the nerve was stained using methyl orange, and a resonant Raman effect was observed when the dyed nerve was illuminated by a laser line at 488 nm. One problem with such technique is that it is invasive the stained nerve dies or loses its vitality in relatively short time. Another problem is the lack of definition or resolution of the resonant Raman spectrum using such observational methods, e.g. for a lobster nerve stained with methyl orange.
In the medical/technological fields it has been proposed to use nucleic acid molecules, such as RNA and DNA molecules, for the storage of information. The storage capacity of a DNA molecule has been estimated to be between 2.sup.18 to 2.sup.20 bits of information. Satisfactory techniques to input and to read out such information have not heretofore been available.